The flywheel bolt solution for 3800 (l67 & l32) swaps (Page 4/5)
Darth Fiero JAN 29, 04:06 PM

quote
Originally posted by BV MotorSports:
Guys, I have been working on this issue for 8 months. I am telling you, 24 ft-lbs for hardware store & ARP cam bolts is not going to cut it on a 3800 with a manual trans.




I've known this for a long time. The ARP SBC cam bolts and hardware store bolts were never designed for this duty. That's why I've only ever used new genuine GM (stock replacement) bolts designed and meant for this job.

That being said, I've wondered whether there is enough material in the crank of the 3800 to drill and tap these holes for bigger bolts. If you've already done it and have run a ton of power thru it with no failures, that answers the question.

[This message has been edited by Darth Fiero (edited 01-29-2016).]

BV MotorSports JAN 30, 12:21 AM

quote
Originally posted by sardonyx247:

If they tend to back out why not just safety wire them like real racecars do?



You could, but I'd venture to say they would then break. Not only are they not TQ'd enough, but the bolt holes in the flywheel are too large if you use a SPEC flywheel.
BV MotorSports JUL 21, 05:59 PM
1k miles, absolutely no problems. You dont even know how happy I am not to have had to pull the trans again.
BadNewsBrendan JUL 30, 09:28 AM
Sorry to bring up an old thread but did this end up holding up? Has anyone else tried this and had success?

After spending probably $150 on the gm camaro flywheel bolts over the last couple years with putting the flywheel on different engines i am sick of these TTY bolts and how difficult they are to find every time. No dealerships i have called have any and can only special order 1 pack of 5 from the warehouse. All the online GM parts sites will let me order them and then cancel the order a few days later or are still "processing" 20 days later. It looks like this is my only option right now.
zkhennings JUL 30, 10:35 AM
This works for a stock Fiero flywheel on an LZ9 as well, I found the same bolts by calling ARP and going through what they offered. I believe these are the same size bolts as stock Fiero flywheel bolts but half a mm longer. There is no re-drilling or re-tapping required though. I also torqued them to 70ftlbs. I have not run the motor yet but can report back when I have some miles on it.
Monstertone AUG 20, 11:56 AM
zkhennings
Can you please be more specific about "this works" & you don't have to redrill the crank? What bolts are you talking about, & have you put any miles on them yet?
BV MotorSports (Steve?) Thanks for going to all the trouble researching & posting this info. Much needed & appreciated.

[This message has been edited by Monstertone (edited 08-20-2021).]

Will AUG 20, 10:54 PM

quote
Originally posted by BV MotorSports:
You will need a 9mm hardened drill bit. A 10mm x 1.00 starting and finishing tap. I ordered these from http://www.mscdirect.com/ since no one has metric drill bits & taps in stock around here. Patience and lots of WD40.



There's no way around needing the metric taps, BUT...
9mm = 0.354
You can use either an S drill at 0.348 or a T drill at 0.358. Either one will be fine.


quote
Originally posted by BV MotorSports:
Drill the flywheel holes 10mm.



Drilling them on-size is a little sketch.
10mm = 0.394
Use a X drill at 0.397 or a Y drill at 0.404. I would actually go with a Y drill. That's still closer than either SAE or ISO close fits for 3/8 or 10mm.

Drill size chart: http://www.carbidedepot.com/formulas-drillsize.htm

S, T, X & Y drills are readily available from just about any hardware store.


quote
Originally posted by BV MotorSports:
Test fit the bolt, make sure it snugs all the way down and is flush! Art stated the surface the bolt compresses needs to be perfectly flat and clean! Make sure you do this. Art said you should also put a slight bevel on the bolt hole opening in the flywheel to give the bolt more surface area to seat against. I followed this advice. Just use a slightly bigger drill bit and give it a quick spin around each bolt hole WITHOUT drilling into them. You just want a slight beveled edge.



The bolts have a radius under the head. The bevel needs to be there to provide clearance for that radius. Damaging that radius can/will cause the bolt to fail.
There is a tool called a countersink that is designed for this purpose. It's like a drill bit, but intended only to cut bevels.


quote
Originally posted by BV MotorSports:
Insert the new bolts using ARP's intructions and torque to 70ft-lbs. I guarantee you will never deal with loose bolts again.




quote
Originally posted by BV MotorSports:
Edit, the right bolt, for the right application, with the correct TQ usually doesn't require thread lock.



Yeah, not so much. As noted, dry installation is not what ARP's instructions say.


quote
Originally posted by Slammed:
You do know 70ftlbs on an M10 12.9 bolt, lubricated, is about 20ftlbs past the recommended maximum torque value... right?



A class 12.9 bolt has a tensile strength of 170,000 PSI. ARP's normal flywheel bolt material has a tensile strength of 200,000 PSI.


quote
Originally posted by BV MotorSports:
I have never used ARP lube on any surface but the bolt head. Thats common sense.



Uhh, no. Common practice when a bolt needs to be lubricated is to lubricate the threads as well as the head. Ever installed a connecting rod bolt? You sure don't torque those with dry threads.

Anyway, the ARP instructions definitely say to use threadlocker on the threads and ARP assembly lube under the head. The 11x1.5mm flywheel bolts I just installed get the same treatment.

There is no value to be derived from incorrect guidance.

[This message has been edited by Will (edited 08-23-2021).]

Turbo-6 AUG 30, 05:16 PM
I am new to this forum and was looking for the proper spot to ask about my issue. and found this question. I have been running the inline 6 version of the Iron Duke motor since 1963 when they came out. People have harmonic problems with 6 cylinder engines all the time since the crank is so long.
My fix has been very simple , put a doll pin between each pair of bolts do not make it go through the flange this keeps the flywheel from trying to shake back and forth, between the bolts you make a tab that the bolts go through and hold the pins in place then the tab has to be long enough to bend the edges over the bolt flats so they can not back out.
Has worked for me .
fierogt28 AUG 31, 11:55 PM
Like Darth mentioned, and I will ask...what's wrong using GM genuine bolts?

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fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

Dennis LaGrua SEP 01, 05:46 AM

quote
Originally posted by fierogt28:

Like Darth mentioned, and I will ask...what's wrong using GM genuine bolts?




The heads of the GM bolts are large and may interfere with the disc on a flat cut flywheel.

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